Catalytic conversion of hydrocarbons



Dec. 13, 1949 A. BELcHETz CATALYTIC CONVERSION OF HYDROCARBONS 4she'ts-sheet 1 Original Filed Nov. 6 1941 MMM. ...hr

ATTORN EYS Dec. 13, 1949 A. BELCHETZ CATALYTIC CONVERSION OFHYDROCARBONS 4 'Sheets-Sheet 2 Original Filed Nov. 6, 1941 ATTORNEYSDec. 13, 1949 A. BELcHETz 2,491,407

GATALYTIC CONVERSION OF HYDHOCARBONS Original Filed Nov. 6, 1941 4Sheets-Sheet 3 Nn vQYnQN @Q Dec. 13,\`1949 A, BELCHETZ 2,491,407

CATALYTIC CONVERSION OF HYDROCARBONS ARNOLD BELCHETZ INVENTOR ATTORN EPatented Dec. 13, 1949 CATALYTIC CONVERSION OF HYDROCARBONS ArnoldBelchetz, Larchmont, N. Y., assignor to The M. W. Kellogg Company,Jersey City, N. J., a corporation of Delaware Original applicationNovember 6, 1941, Serial No.

418,005. Divided and this application February 12, 1945, Serial No.577,439

11 Claims. 1

The present invention in its specific aspects relates to the catalyticconversion of hydrocarbons into lighter hydrocarbons of lower-boilingpoint or hydrocarbons otherwise altered in structure. In certain of itsaspects the invention is particularly concerned with hydrocarbonconversions such as the catalytic conversion or cracking of high-boilingpetroleum oils to low-boiling products within the gasoline boilingrange.

The invention is especially concerned with the catalytic conversions ofhydrocarbons involving two stages, a conversion stage wherein thehydrocarbons undergoing treatment are contacted with the catalyst underconditions adapted to effect the desired conversion, and a regenerationstage wherein the carbonaceous deposit formed on the catalyst during theconversion stage is eliminated. In its preferred aspect, my inventioncontemplates particularly an improved process involving a conversionstage wherein vapors of the hydrocarbons undergoing treatment arecontacted in a conversion zone with particles of a suitable catalyst;and a regeneration step wherein the used catalyst particles, afterseparation from the gaseous conversion products, are contacted with anoxygen-containing gas in a regeneration zone under suitable conditionsto regenerate them by burning off deposited carbonaceous material.

This method of catalytically converting hydrocarbons has certainadvantages arising particularly out of the relative intimacy of contactwhich it affords between the catalyst particles and the contacting gasboth in the conversionl and regeneration operations and the continuouscharacter of the operation. It exhibits.- however, variousdisadvantages, the elimination of which is one of the primary objects ofmy invention. One of these disadvantages is the problem of maintainingthe temperature of the regeneration reaction within desired limits andin such manner as to eliminate the' carbonaceous deposit on the catalystto the desired extent without overheating of the catalyst.

The present application is a divisional application of my copendingapplication Ser. No. 418,005, filed November 6, 1941, now U. S. PatentNo. 2,369,523, issued February 13, 1945, and the latter application inturn being a continuation-in-part of my copending application Ser. No.343,222 led June 29, 1940. In the latter application, I have disclosedseveral modifications of precesses for controlling the temperature ofthe catalyst regeneration zone Within desired limits by the charging ofcatalyst to the regeneration zone in a predetermined and controlledrelationship with respect to certain of the variable operating con-Aditions involved including the quantity of feed charged to theconversion zone. The present application is directed particularly tocertain modications disclosed in said copending application` involvingthe feature of controlling the temperature of the regeneration zone bycooling a portion of the catalyst withdrawn from the regeneration zonein a zone distinct from the conversion zone and returning the cooledcatalyst to the regeneration zone for the purpose of temperature controltherein.

The foregoing and various other features and advantages of the inventionwill be apparent from the following detailed description thereof givenwith reference to the appended drawings which illustrate suitableprocess flow and arrangement of apparatus f orits practice.

Figure 1 illustrates a suitable arrangement of apparatus and processflow involving the feature of introducing cooled regenerated catalyst tothe regeneration zone for temperature control therein as applied to thecatalytic conversion of highboiling hydrocarbons to low-boilinghydrocarbons within the motor fuel boiling range.

Figure 2,is a modied embodiment generally similar to Figure 1 andinvolvingthe additional feature of'recycling-used catalyst to theconversion zone.

Fig. 3is a modified form of process ow involving the feature ofrecycling cooled regenerated catalyst in a plurality of streams.

Fig. 4v is a modified embodiment generally similar to Fig. l andinvolving the feature of maintaining the velocity of vapor flow withincertain preferred ranges.

Referring to Fig. 1, a suitable feed, for example a cracking stock suchas a vaporized petroleum gas oil heated to a suitable temperature, isintroduced through transfer line l2 leading from a conventional pipestill or other suitable source not illustrated. The feed vapors intransfer line l2 may be advantageously combined with a recycle oilfraction introduced through line I4, the

combined streams passing to the conversion stage through line I5. Theoil passes through line I into pipe I6 constituting an extension of theconversion reactor I'I. Hot preheated catalyst is supplied fromcollecting or surge drum I8 by helical feeder I9 and mixed with the oilin pipe I6. The upper surface of the body of catalyst in drum I8 isindicated by dotted line 60. Sufficient steam or other suitable gas toinitially disperse the catalyst as discharged from feeder I9 ispreferably introduced through line 20. Steam or other suitable gas maybe supplied in greater quantities through line when required. Operatingconditions such las the ratio by weight of the catalyst to fresh feedstock may be maintained and regulated as set forth in detailhereinafter. The gaseous mixture of feed stock, catalyst and steam flowsupwardly through reactor I1 during which flow conversion or cracking ofthe oil to the desired extent occurs.

Reaction products pass from the top of reactor II to a suitableseparator system to separate the catalyst from the vaporous reactionproducts. That shown comprises a settling tank 2| in which the majorproportion of the suspended catalyst is separated, the separatedcatalyst flowing by gravity from the bottom of tank 2| through conduit22 to the top of a steam stripper tower 23 and the vapors containing arelatively small fraction of ne catalytic material are withdrawn at thetop through line 24. These vapors pass through line 24 to a suitableseparator such as a cyclone type of dust collector 25 wherein most ofthe remaining suspended catalyst is separated and then passed to tower23 by gravity now from the bottom of the separator through line 26.

Tower 23 serves to displace hydrocarbon vapors contained in the voidsbetween the particles of catalyst and is suitably provided with baffles2'I to effectively expose the catalyst passing downwardly therethroughto the displacing action of a countercurrently flowing current of steamintroduced at the base of the tower through line 28. Steam containingthe oil vapors displaced from the catalyst is withdrawn from the top ofthe tower through line 29 and combined with the vapor stream'from tank2I. Used catalyst falls from the bottom of tower 23 into a surge drum30. The gaseous suspension Withdrawn from separator 25 containing thegaseous conversion products, steam and a small residual amount of usedcatalyst is passed through line 3I to a suitable type of fractionator 32wherein a low-boiling fraction such as gasoline and fixed gases may beseparated from the high-boiling products such as light and heavy cyclegas oils. In the fractionator 32 the conversion products may, forexample, be fractionated into a low-boiling fraction including gasolineand fixed gases withdrawn as overhead product from the fractionatorthrough line 33, an intermediate product such as light gas oil withdrawnas a side cut through line 34, and a residual high-boiling fraction suchas heavy recycle gas oil withdrawn through line 35, cooled in coolingcoil 6I, and pumped to storage through line 38.

In the bottom of fractionator 32 suitable means may be provided forseparating residual catalyst present in the vapors introduced throughline 3I. As shown, these means comprise a line 31 through which aportion of the high-boiling fraction withdrawn through line 35 isreturned to the fractionator over bailes 36 which deflect the vaporsfrom line 3I into intimate contact with the returned fraction whichconsequently adsorbs or scrubs out residual catalyst present in thevapor. After passing over baiiles 36 the scrubbing liquid with theresidual catalyst suspended therein collects in the bottom offractionator 32 from which it is withdrawn through line 39 and pumped bypump 40 into line I4 for utilization as a recycle oil, as previouslydescribed.

Used catalyst is fed from drum 30, in which the upper surface of thecatalyst mass is indicated by dotted line 62, by screw feeder 4I to pipe42. A further stream of catalyst is introduced into line 42 from line83, the latter stream consisting of cooled and previously regeneratedcatalyst, the quantity thus introduced being preferably regulated ashereinafter described. A suitable quantity of air is introduced to line42 through line 43 supplemented if desired by steam introduced throughline 45. The mixture of used and recycled catalyst is carried throughline 42 by the current of oxygen-containing gas injected through line 43to regeneration or combustion chamber 44 in which combustion of thecarbonaceous deposit on the spent catalyst occurs during the passage ofthe catalyst therethrough.

Combustion gases bearing the regenerated catalyst pass from chamber 44into a suitable recovery system for separating the catalyst. Inaccordance with the embodiment shown in Fig. 1, the stream ofregeneration gas carrying the regenerated catalyst upon leaving theregeneration zone 44 is split into two streams, one portion beingby-passed through valve II to line 10, and the other portion passingthrough valve to separator 46. In separator or settling tank 46 most ofthe catalyst present in the stream introduced thereto is separated andilows downwardly therefrom through conduit 4l' to surge drum I8. Theseparated gases containing a small residual amount of catalyst finesleave separator 46 at the top through line 48 and pass to a cyclone typeof dust collector 49, wherein substantially complete separation of thecatalyst is effected. The separated catalyst from collector 49 thenflows downwardly through line 5|] and is combined with the initiallyseparated catalyst in drum I8 from which it is fed to the conversionstage by feeder I9. Drum I8 and feeder I9 may be suitably provided withheat insulation material to obviate loss of heat by the regeneratedcatalyst in its passage therethrough.

In the practice of my invention the quantity and temperature ofregenerated catalyst recycled to the regeneration zone through line 'IIImay be suitably determined by the application of a generalized formula.In xing the ratio (r), by weight, of the total catalyst charged to theregeneration zone relative to the fresh gas oil charged to theconversion zone for any particular oil and extent of conversionrequired, this ratio is determined under the other given or fixedoperating conditions concerned in a manner adapted to assure thepresence of the cool recycled catalyst in suflicient amount to absorb adenite minimum amount of the heat of regeneration by the application ofthe following formula:

In this formula r represents the catalyst-to-oil weight ratio as definedabove; the symbol C, the fraction of the gas oil or other hydrocarboncharged, converted to coke or carbonaceous material and deposited on thecatalyst during the conversion; H, the heat of combustion of the coke orcarbonaceous material expressed in B. t. u.s per lb.; S, the specificheat of the catalyst; T1, the maximum temperature in degrees Fahrenheitto which the catalyst is subjected during regeneration and thetemperature of the catalyst upon withdrawal from this zone which isdeterminable by the deactivation temperature of the particular catalyticmaterial involved, i. e. the temperature in excess of which the catalystmay not be heated without permanent and substantial injury to itscatalytic activity; T2, the temperature in degrees Fahrenheit of thetotal catalyst entering the regeneration zone represented by theweighted average temperature of used catalyst and cooled recycledcatalyst entering the regeneration zone; and K, a coefficient having alower limit determined by the extent to which expedients :other than theheat absorption capacity of the catalyst may be employed to dissipatethe heat of regeneration.

The quantity of catalyst recycled to the regeneration zone and thetemperature thereof is preferably controlled in such manner that thevalue of K in the above equation is in excess of 0.2 and preferably inexcess of 0.5, and may suitably be about 0.8 or even higher.

The preferred quantity and temperature of recycled catalyst may beexpressed directly by a modification of the above basic equation asfollows,

R C'HK-RS(T1T3) MT1-T4) In the above equation the symbol R representsthe ratio by weight of the regenerated catalyst charged to theconversion zone to the weight of oil charged to the same zone; T3, thetemperature of the used catalyst on entering the regeneration zone fromdrum 30; T4, the temperature of the recycled catalyst on entering theregeneration zone from drum 16; and R1, the ratio by weight beween thequantity of catalyst recycled to the regeneration zone, and oilintroduced into the conversion zone. The other symbols have the samemeaning as in the basic formula or equation, and the coeicient K issubject to the same preferable values.

The fraction of regenerated catalyst for temperature control determinedas given above, passes through an indirect heat exchanger 12 throughwhich a cooling medium is circulated through lines 13 and 14. The cooledsuspension of ue gas and catalyst then passes through line 15 into aseparating zone 16 wherein flue gas is taken overhead through line 18and separated catalyst is collected in the lower portion as indicated byline 11. Any catalyst remaining in the flue gas withdrawn overhead maybe separated by a cyclone separator 19 or similar device and returnedthrough line 8l to zone 16. Catalyst is fed from zone 16 by means of ascrew conveyor 82 and suspended in air supplied through line 84 andcarried through line 83 to transfer line 42 wherein it is mixed withused catalyst supplied by screw conveyor 4|.

Any type of catalyst suitable for effecting the desired conversion maybe employed in the practice of my invention. For the conversion orcracking of high-boiling fractions such as gas oil to low-boilingfractions such as gasoline, I regard cracking catalysts of thealumina-silica type as especially suitable, this term being inclusive ofcracking catalysts such as certain types of activated clays orsynthetically produced mixture'or compounds of alumina and silica. The

circulated catalyst may be composed entirely of the active catalyticmaterial and is preferably predominantly composed thereof. However, the5 active catalyst may be associated with supports, extenders or soliddiluents which for the purpose of applying the formulae previously givenare to be -considered as part of the catalyst, since such soliddiluents, etc., will function in a manner similar to the active part ofthe catalyt relative to the absorption of heat in the regeneration zone.

Referring to the modified form of flow illustrated in Fig. 2, this issimilar to that of Fig. 1 in that it involves the recycling of cooledregenerated catalyst to the regeneration zone, but also involvesadditional novel features including the recycling of catalyst to theconversion Zone -without intervening regeneration thereof.

Regeneration gas containing regenerated catalyst suspended therein iswithdrawn from regenerator 44 through line 86 and split into twostreams, one stream passing through recycle line 10 controlled by valve1|' and the other stream passing to the conversion side of the system byline 81 controlled by valve 80.r The recycled catalyst passing throughline 10 as in the case of the embodiment shown in Fig. 1, is returned tothe initial part of the regeneration Zone after cooling and separationfrom the flue gas carrier by means similar to those shown in Fig. 1 anddesignated by corresponding primed reference numerals.

The fluid suspension of regenerated catalyst passing through line 81 maybe passed directly to settling drum 88 through valve 89 and line 90, orall or a portion thereof may be bypassed through valve 9| and line 92through a suitable cooler or heat exchanger 93 through which a suitablecooling or heating duid is circulated through lines 94 and 95. Inpassing through exchanger 93 the temperature of the catalyst is broughtto that most suitable for the particular conversion reaction con- 45cerned. The fluid suspension passes from line 90 into settling drum 88wherein most of the catalyst is separated from the flue gas and settlesinto the bottom of the drum. Flue gas bearing a residual amount ofsuspended catalyst 50 passes overhead from drum 88 through line 96 intoa suitable separator such as cyclone separator 91 wherein substantiallycomplete separation of the residual catalyst is effected and theseparated catalyst returned from the bottom 55 of the cyclone throughline 98 to drum 88.

From drum 88 the regenerated catalyst is fed into a stripping tower 99by suitable feeding means |00. In tower 99, the catalyst ows downwardlyover baflies countercurrently to 00 a current of steam introducedthrough line |02.

The stripping steam bearing with it any oxygencontaining gasespreviously entrained with the regenerated catalyst passes overheadthrough line |03 into cyclone |04 wherein any catalyst 65 particlesentrained with the steam are separated and pass from the bottom of thecyclone to an accumulator drum and are then returned to the bottom oftower 99 by suitable feeding means |06. The stripping operation servesto 70 remove any oxygen-containing gases present in the regeneratedcatalyst which 4might be detrimental in the subseqeunt conversionreaction.

Stripped catalyst is fed from the bottom of tower 99 by suitable feedingmeans |01 into line 75 |08 wherein it is suspended in the vapors of thefeed stock undergoing treatment and the suspension introduced into theconversion ref actor |09. Additional catalyst may be added at this pointby means of feeding means ||0. Reaction products are withdrawn from thetop of reactor |09 through line and passed to a suitable settling drum 2wherein most of the suspended catalyst drops out of suspension into thebottom of the drum. The conversion products pass overhead from drum ||2through line ||3 and residual catalyst is separated therefrom in cyclone||4 from whence it is returned to drum ||2 through line ||5. Thehydrocarbon conversion products are withdrawn overhead from cyclone |`|4through line |50 and passed to a suitable fractionating system such asthat indicated on Figure 1. From drum ||2 a portion of the used catalystmay be recycled to the conversion zone by feeding means without anyintervening stripping operation, the proportions introduced into thereaction zone of regenerated catalyst from feeding means |01 andrecycled catalyst from means ||0 being adjusted to provide any desiredactivity of catalyt in the reactor.

Used catalyst is fed from the bottom of drum ||2 into a suitablestripping system by feeding means ||6 at the same rate that regeneratedcatalyst is fed to the reactor by feeding means |01. The strippingsystem is similar to that described in connection with the strippingtower 99 and includes a stripping tower and a fines recovery systemincluding cyclone I |8, accumulator drum ||9 and return feeding means|20. In passing through tower the used catalyst is stripped ofhydrocarbons entrained therewith which pass out from the system withthe-steam by line |2I, and may be recovered therefrom by any suitablerecovery means. Stripped used catalyst is fed from the bottom of towerby suitable feeding means |22 and suspended in regeneration airintroduced through line |23 and the suspension then passed through line|24 into the regenerator 44. Recycled catalyst may be introduced intothe regenerationzone by vmeans 82', the regeneration steps thereafterbeing similar to those described in connection with Figure 1.

Referring to Figure 3, this illustrates a modification of theregeneration system shown in Figure 2, the distinctive feature being therecycling of cooled regenerated catalyst to the regeneration zone in aplurality of streams at spaced points in said zone. As in the case ofFigure 1 the regeneration gas vbearing the regenerated catalyst is splitinto two streams, one passing through line |3| to the conversion systemand the other through a recycle line |32, the quantity of suspension ineach stream being controlled by valves |33 and |34, respectively. Thesuspension of regenerated catalyst passes through recycle line |32 intosettling drum |35 wherein most of the catalyst settles `out into thebottom of the drum, and any-residual catalyst carried out overhead fromthe drum by the ue gas is separated in a suitable cyclone separator |36and returned to drum |35. Used catalyst from the conversion stage issupplied to the regeneration stage by suitable feeding means |38 and issuspended in part of the total air required for regeneration suppliedthrough line |39, the quantity of air supplied at this point beingcontrolled so that the combustion which occurs in zone A will bring thecatalyst to a temperature approximating the maximum safe regenerationtemperature when it reaches the point at which cool recycled catalyst isrst introduced. A plurality of streams of recycled regenerated catalystis returned from drum |35 to the regenerator by means of pumps |40, |4|and |42 through lines |43, |44 and |45, respectively. Air is injected atthe outlet of each of these pumps to convey the regenerated catalystthrough coolers |46, |41 and |48, respectively. Using a plurality ofstreams as shown, the recycled catalyst is injected into the regeneratorat a series of spaced points so that each injection of the cooledcatalyst will drop the temperature in the regenerator by only arelatively small amount. Air is preferably introduced with each streamof recycled catalyst in amount such that the catalyst will beapproximately at the maximum safe regeneration temperature when itreaches the next catalyst injection point. By this means the burning ofthe coke is accomplished at a high temperature level approaching themaximum safe regeneration temperature throughout the regenerator, andwith the result that the time required for coke combustion is decreased.The diameter of the regenerator may be enlarged after any catalystinjection point as shown to increase its volume by an amountcorresponding to air added at this point, thereby maintaining uniformvelocity of flow. In addition to the flexibility of temperature control,this system has the added advantage that the injection of the cooledrecycle catalyst will not drop the temperature in the regenerator to apoint where combustion of coke on the partially regenerated catalyst maycease.

In the practice of my invention, the upward velocity of the regenerationgas through the regenerator may be varied over a wide range withattainment of reasonably satisfactory results. For a given quantity ofgas introduced, this gas velocity will be dependent upon thecross-sectional area of the regenerator and varies inversely therewith.A range of gas velocity from about 1 to 25 feet per second is regardedas satisfactory in most instances. At the higher order of volicities thecatalyst particles are carried along with the gas at a speed somewhatlower but approximating that of the gas, and accordingly the periodduring which the catalyst particles are in the regenerator isapproximately the same but somewhat greater than the period of contactof the gas molecules with the catalyst. Also, under such condition thedirection of movement of the catalyst particles upward through theregenerator is largely linear, as in the process ow of Figure 3. Certaindistinctive advantages are obtained by the practice of my inventionunder conditions wherein a relatively low upward velocity of theregeneration gas through the regeneration zone is maintained, forexample, a velocity of about 1 ft. per second, and generally velocitiesin the range of about 0.5 to 6 ft. per second and preferably within therange of 0.5 to 3 ft. per second. These velocity ranges are especiallydesirable with powdered catalyst consisting of small particlesindiscriminately sized Aand smaller than about microns. With widelydifferent sized particles variation in these velocity ranges may bedesirable. The conditions and advantages of the invention as thuspracticed are illustrated by the process flow shown in Figure 4.

Referring to Figure 4, catalyst particles such as a powdered crackingcatalyst are introduced through the valve |89 of a catalyst standpipe|8| into a stream of the feed vapors traveling at a relatively highvelocity through the reactor inlet line |52. Both the catalyst andvapors are heated prior to their mixture in line |52 to a temperaturesuitable for the subsequent conversion. Vaporized feed may be suppliedto line |52 by a transfer line |53 leading from a pipe still heater orother suitable source of hot vaporized feed stock. In certain instances,the hydrocarbon feed may be introduced through line |53 entirely orpartially in the liquid phase and the necessary vaporization producedupon the mixture of hot catalyst therewith. Catalyst thus introduced ispicked up by the vapors and carried therewith through line |52 into aconical inlet |55 in the lower part of reactor |56. Reactor |56 is avessel in the form of a cylinder or other suitable shape, having arelatively great cross-sectional area compared with the cross-sectionalarea of the vapor inlet line |52, and these relative proportions cause acorresponding reduction in the velocity of the vapors after theirpassage from inlet line |52 into the reactor |56. The velocity of thevapors in reactor |56 is preferably maintained relatively low and withinsuch limits as previously given so as to produce a concentrated denseturbulent phase of the catalyst in this zone which state mayconveniently be designated as uidized This luidized condition, ingeneral, is characterized by the relatively high concentration ofcatalyst measured in terms of the quantity of catalyst per unit Volumeof reactor space, and by the low velocity of reactant vapors upwardlythrough the reactor. This condition is further characterized by theextensive turbulence or internal recycling of the catalyst particlesthroughout the reaction zone so that the temperature of the zone,regardless of whether the reaction involved is endothermic or exothermictends towards uniformity throughout the zone and hence is characterizedby the absence of a substantial temperature gradient. Also due to thisextensive turbulence the particles tend to reach an average compositionwith respect to their carbon content throughout the zone regardless ofwhether the reaction concerned is one involving deposition ofcarbonaceous material or its removal. The level of the relatively denseiiuidized phase is preferably maintained at the upper portion of thereaction zone as indicated by line |90.

The reactant vapors travel upwardly through the reactor in contact withthe fluidized catalyst and during this period of contact undergo thedesired conversion. Operating conditions in the reactor determined byvariables such as the dimensions of the reactor, and the temperaturesand rates at which reactant vapors and catalyst are supplied thereto,are maintained within such limits as to bring about the desired qualityand extent of conversion.

The Vaporous reaction products are withdrawn from the upper part of thereactor through a suitable outlet pipe or cone |51. The used or spentcatalyst may be separated from the Vaporous conversion products by anyone of several suitable methods. According to that illustrated in Figure4, the vapors pass from the upper portion of the reactor into theconical outlet |51 of decreasing cross-sectional area wherein theirvelocity is progressively increased and then into an outlet pipe |56 ofrelatively restricted cross-sectional area compared with that of thereactor. The vaporous conversion products mixed with spent catalyst passthrough the outlet pipe |58 at a relatively high velocity into asettling chamber or collecting hopper |59 of such cross-sectional areathat the velocity of the vapors therein is preferably of about the sameorder of magnitude but may be more or less than the vapor velocity inreactor |56. A baille |60 is preferably interposed directly in the pathof the vapor mixture passing from pipe |58 whereby the mixture isdirected laterally and downwardly thus functioning to propel catalystparticles present in the mixture out of the path of the vapor flow intoa quiescent collecting zone defined by the outer walls of the outletcone |51 and outlet pipe |58 and the lower inner walls of the settlingor collecting hopper |59. Catalyst thus separated is withdrawn throughsuitable means such as catalyst standpipe |6| opening into the lowerpart of the collecting zone. A quantity of catalyst is preferably leftat all times in said zone to maintain a level of catalyst therein at asubstantial distance above the spent catalyst outlet opening asindicated by dotted line |62. Vaporous conversion products are withdrawnfrom the upper part of the collecting hopper through line |63 mixed witha relatively small portion of the catalyst originally present in themixture passing through pipe |58.

Residual catalyst left in the Vaporous conversion products leavingthrough line |63 is separated in a suitable recovery system such ascyclone separators or the like, and may be returned to the spentcatalyst separated in chamber |59 through line |64.

A suitable stripping medium such as steam is introduced through a line|65 having suitable vapor distributing means |66, in the bottom of themass of catalyst in the collecting zone to strip or displace hydrocarbonvapors absorbed thereon or entrained therewith and to maintain the massin an aerated flowable condition. While only one such line |65 forintroduction of the stripping medium is shown, it is to be understoodthat any suitable number may be employed and be so distributedthroughout the collecting chamber as to assure the required strippingand aerating effects. The quantity of stripping steam is preferably suchthat its velocity in the collecting zone is low, that is, of the orderof about 0.1 to 0.3 ft. per second. The stripping medium and strippedoil vapors pass out of chamber |59 overhead through line |63 togetherwith the Vaporous conversion products.

As illustrative of operating conditions suitably maintained in theconversion zone |56 in the cracking of high-boiling hydrocarbons togasoline, reference is made to the data tabulated in the following Table1 which sets forth conditions suitable for a large scale commercial unitfor a given type of charging stock and capacity.

Table 1 Gas oil feed (31.1 API), bbl/day 10,000 Steam feed, lbs/hr13,360 Reactor dimensions (a) ht., ft 28 Reactor dimensions (b) dia., ft15 Feed weight ratio of regenerated catalystto-oil in line |52 (R) 5Reactor temperature, inlet cone |55, F 933 Reactor temperature(substantially throughout), F 900 Reactor pressure, inlet cone 55,lbs/sq. in-- 13 Reactor pressure, outlet cone |51, lbs/sq.

in 9.6 Vapor velocity,l inlet, ft./sec 1.48 Vapor velocity, outlet,ft./sec 2.45 Ratio of weight of oil fed/hr. to weight of catalyst inreactor (w./hr./w.) 2.6

1l Oil vapor, contact time, seconds 13. Catalyst time, seconds 290Catalyst concentration, lbs/cu. ft.:

(a) Inlet line |52 0.98 (b) Reactor 13 (c) Reactor outlet, line |58 0.6

In conveying the spent catalyst from the spent catalyst collecting zoneto the regeneration zone suitable provision is made for any differencein pressure between these zones. A somewhat higher pressure is normallypreferably maintained in the bottom or inlet portion of the regenerationzone than the pressure maintained in the collecting zone, and a head ofsuitably aerated or uidized catalyst is preferably maintained in theoutlet standpipe 6| of a suicient magnitude to balance or exceed thisdinerential pressure. For this purpose spent catalyst owing throughstandpipe |6| is maintained in condition in which it has the flowcharacteristics of a liquid by introducing in suitably regulated amountsan aerating medium such as steam through lines |61 at the bottom of andat other suitably spaced points along the length of pipe From the bottomof standpipe I6| spent catalyst is fed under the influence of thepressure head maintained therein and the pressure head provided by themass of aerated catalyst in chamber |59 through a suitable feeding meanssuch as a valve |68 into the regenerator inlet line |69.

Spent catalyst thus introduced is mixed with air or other suitablecarrying medium such as steam introduced into pipe |69 by line |10. Incase air is employed, the quantity introduced is so controlled that thecombustion of the spent catalyst in line |69 is not suicient to raisethe temperature of the catalyst beyond the maximum safe regenerationtemperature.

The mixture of hot spent catalyst and carrying medium flows through line|69 into an inlet cone |16 at the bottom of the regenerator |1| where itmeets and mixes with a stream of relatively cool recycled regeneratedcatalyst and air from cooler |12 and passes therewith upwardly throughthe regeneration chamber |1|. Operating conditions in the regenerationchamber or zone |1| are suitably maintained to provide a conditionsimilar to that maintained in the reaction zone with respect to auidized condition of the catalyst. This condition similar to thatmaintained in the reactor is characterized by the relatively largeconcentration of catalyst and low gas velocity maintained in theregeneration zone. Also, as in the case of the conversion Zone, a highdegree of turbulence and internal recycling may be maintained in theuidized mass whereby its temperature and the average carbon content ofthe catalyst is substantially uniform throughout the reactor. The levelof the relatively dense uidized phase is preferably maintained at theupper portion of the reaction zone as indicated by line |9|. During thecourse of the passage of the spent catalyst through regeneration chamber|1| combustion of the carbonaceous deposit thereon is effected to therequired extent at an elevated temperature maintained below the safemaximum regeneration temperature by means of the cooled recycledcatalyst.

Gaseous regeneration products (flue gas) and regenerated catalyst passfrom the upper part of the regenerator through an outlet |13 and into aseparator |14 similar in design and mode of operation to separator |59,described in connection with the reactor. The major portion of theregenerated catalyst is separated and collected in a collecting zone atthe bottom portion of the regenerated catalyst collecting hopper |14,and the gaseous combustion products together with a relatively smallamount of regenerated catalyst pass out overhead from chamber |14through line |15 to a suitable recovery system. Catalyst recovered fromthe flue gas leaving through line |15 may suitably be returned to hopper|14 through line |16.

Suitable means |11 and |18, similar to pipe |65 and distributor |66, areprovided in the lower portion of hopper |14 to introduce a suitablemedium such as steam to strip and displace ue gas absorbed or entrainedwith the regenerated catalyst and maintain the separated catalyst in anaerated owable state. As in the case of the reactor a level of separatedcatalyst indicated by dotted line |19 is preferably maintained at asubstantial distance above the catalyst outlet lines.

Regenerated catalyst is withdrawn from separator |14 in a split stream,a portion being sent through regenerated catalyst recycle line |80, andanother portion through regenerated catalyst line |8| leading to theconversion or reaction system. Both catalyst outlet lines |80 and |8|are suitably pressure standpipes similar to standpipe |6| in that theyare provided with means for introducing an aerating medium at suitablepoints along their length so as to maintain the catalyst owingtherethrough in a condition wherein it has the ow characteristics of aliquid, such means being lines |82 leading into recycle line |80 andlines |83 leading to catalyst outlet line |8|. The quantity of catalystWithdrawn and recycled through line |80 and the cooling thereof iscontrolled so as to maintain the temperature in regeneration Zone |1|within required limits as may be determined by the application of themathematical formulae previously given.

Regenerated recycle catalyst is fed from the bottom of standpipe |86through a suitable feeding means such as a slide valve |84 into an inletline |85 leading to a heat exchanger or catalyst recycle cooler |12.Regenerated catalyst thus introduced is picked up by air introduced intoline |85 through line |86, the quantity of air thus introduced beingsuiiicient together with any air introduced through line |10 to effectcombustion to the required extent in the regenerator |1|. From line |85the mixture of air and regenerated catalyst passes through exchanger orcooler |12 wherein the temperature of the recycled catalyst is loweredto the required degree by indirect heat exchange with a cooling mediumcirculated through the exchanger by lines |81 and |88.

Regenerated catalyst is fed to the conversion system from standpipe |8|through a suitable feeding means at the bottom thereof such as a slidevalve |89 into the stream of vapors to be converted passing through line|52 as previously described.

To illustrate operating conditions suitably maintained in theregeneration zone in the practice of my invention, reference is made tothe data tabulated in the following Table 2 wherein regeneration zoneoperating conditions are shown corresponding to the conversion runstabulated in Table 1.

Table 2 (R1) 13.82 Feed weight ratio (R-l-Ri) of total fed toregeneration zone-to-oil (r) 18.08 H, the heat of combustion of thecarbonaceous deposit in B. t. us 16,400 S, the specic heat of powderedalumina-silica cracking catalyst 0.22 Inlet temperature to regeneratorby line |69, spent catalyst, F. (T3) 900 Inlet temperature, recycledcatalyst,

F., by line |80 (T4) 840 Temperature, weighted average of mixturerecycled and spent catalyst, F., through lines |80 and |69 (T2) 850Temperature, regeneration chamber (substantially throughout), F., andcatalyst withdrawn through lines ||8| and |80 (T1) 1,000 Regenerationdimensions:

(a) Height, ft 50 (b) Dia., ft 18 Regeneration velocity:

(a) Base 1.62 (b) Top 2.59 Air feed, lbs/hr 88,350 Catalystconcentration regenerator,

lbs/cu. ft 20 Weight per cent of coke based on oil feed (100C) 4.85 Cokeper cent by weight on spent catalyst 1.3 Carbon per cent by weight onregenerated catalyst (lines |80 and |8|) 0.7 Catalyst contactl time,seconds 352 Pressure in regenerator, lbs/sq. in.:

(a) Inlet cone 16 (b) Outlet cone 9 Value of symbol K 0.75

In the above example, combustion in the regeneration zone Was effectedin such manner that the carbonaceous deposit on the spent catalyst wasonly partially removed, that is, reduced from about 1.3% to about 0.7%by weight of the catalyst.

In the above example it is to be noted that the value of K is maintainedin excess of 0.5 and consequently exemplifies the practice of theinvention in accordance with the preferred range for this value. It willbe further apparent that the quantity and temperature of regeneratedcatalyst recycled to the regeneration zone through line |80 pursuant tothe above example conforms to the application of either of the twogeneralized equations given in the foregoing.

In accordance with the first generalized equation the feed weight ratio(r) of the total catalyst charged to the regeneration zone relative tothe oil charged to the conversion zone is determined by the followingequation CH "S (T1-T2) K Substituting in the above equation for thesymbols the numerical values utilized in the above example (the valuegiven for T2 being approximated) gives the following .0485 X 16,40QX0.75 0.22 (100G-850) Pursuant to the second generalized equation whichis a modification of the first the preferred quantity and temperature ofrecycled catalyst is given by applying the following Substituting in theabove equation the numerical values for the. symbols utilized in theabove example gives the following .0485X 16,400X .75 -5 X .22 (1000-900).22 (1000- 840) It is to be noted that regeneration is eiected pursuantto the above example without employing the conventional expedients forcontrolling the temperature of the catalyst during regeneration such asthe provision of cooling surfaces within the regeneration zone ordilution of the regeneration air with large quantities of an inert gas.e

The maintenance of a definite minimum concentration of carbonaceousmaterial on the catalyst .as exemplified by the above example, hasimportant distinctive advantages. It assists in the regenerationreaction since the rate of combustion is accelerated and more readilycon- 4trolled by the presence of an amount of carbonaceous material inexcess of that which is to be removed by combustion. The retention ofresidual carbonaceous material also makes it possible to discharge theregeneration combustion gas with a relatively low percentage or in somecases, entirely free of oxygen, and the gas is thus better adapted foruse for various purposes.` Also, in .certain instances, particularly i'ncatalytic cracking in the presence of alumina-silica type of crackingcatalyst such as Super-Filtrol, the conversion reaction is facilitatedby the presence of a small amount of residual carbon and in mostinstances the advantages obtained in regeneration by the maintenance ofva residual carbon concentration will outweigh the disadvantages if any,resulting in the conversion stage. The residual carbon concentrationmaintained may depart somewhat from that given in the foregoing examplewherein` a Super-Filtrol". type of alumina-silica cracking vcatalyst wasemployed, Preferably,

this permissible range is confined to about 0.5% to 2.0 by weight of thecatalyst.

As an alternative, the process flow shown in Figure 4 may be modifiedto-the extent of having line and/or line |8| connect directly With theregeneration zone at a point below the level |9| of the dense catalystphase. By this arrangement all but a small portion of theregeneratedcatalyst is Withdrawn directly from the regeneration zone andonly a relatively small quantity withdrawn overhead with the flue gaspassing through line |15. In this alternative arrangement the highvelocity outlet cone |13 may be omitted.

'Although my invention is especially Well exemplified and advantageousas applied to the catalytic cracking of high-boiling hydrocarbons tolower boiling hydrocarbons within the gasoline boiling range, it may beapplied with advantage to gas-solid contact processes generally and toother hydrocarbon conversions such as the catalytic reforming of naphthafractions and to catalytic hydrocarbon conversion reactions generally,as will be apparent to those skilled in the art.

From the foregoing it will be apparent that the process thereindescribed accomplishes the objects of my invention, and that variousfeatures thereof may be utilized to advantage either conjointly orseparately. It will further be readily apparent to those skilled in theart that while the invention has been illustrated and described withrespect to a preferred operation and examples, and with reference tosuitable apparatus for its practice, the invention is not limited tc Lsuch exemplications but may variously be practiced and embodied withinthe scope of the claims hereafter made.

I claim:

1. The method of regenerating spent catalyst fouled with carbonaceouscontaminants in a systern wherein the nely divided spent catalystsuspended in a gas moves continuously through a plurality ofregeneration zones which comprises, partially regenerating the movingcatalyst in one zone, thereafter admixing cool regenerated catalyst withthe partially regenerated catalyst, treating said mixture in anotherzone with a gas containing free oxygen under conditions such as to causefurther substantial combustion of the carbonaceous contaminants andfurther regeneration of the partially regenerated catalyst.

2. The method of regenerating finely divided spent catalyst fouled withcarbonaceous contaminants in a system wherein the spent catalyst movescontinuously while suspended in air serially through a plurality ofregeneration zones and is partially regenerated by the removal of afraction only of the total carbonaceous contaminants in each of saidzones which comprises limiting the fraction of contaminants removed inone of said zones to an amount removable by. combustion with the oxygenof the suspending air Without exceeding the maximum safe catalystregeneration temperature and without substantial removal of heat fromsaid zone by extraneous cooling means, removing another fraction of saidcarbonaceous contaminants by combustion with the oxygen of thesuspending air in another of said zones under conditions wherein removalof heat by extraneous cooling means is necessary to prevent atemperature rise in the catalyst in excess of the maximum saferegeneration temperature, and recycling previously regenerated andcooled finely divided catalyst to the latter zone to maintain thetemperature thereof within required limits.

3. In a catalytic process of cracking hydrocarbon oils wherein apowdered cracking catalyst is alternately suspended in and contactedwith vapors of the oil thereby becoming contaminated with carbonaceousdeposits and thereafter the contaminated catalyst particles aresuspended in and contacted with an oxygencontaining gas to remove thecarbonaceous deposit by combustion, the improved method of removing thecarbonaceous deposits comprising withdrawing hot contaminated powderedcatalyst directly from the cracking zone and commingling air therewith,passing the resultant combustion-supporting suspension upwardly throughan initial regeneration zone in which the temperature of the catalyst ispermitted to rise to a level approximating but below the maximum saferegeneration temperature and partially removing the carbonaceouscontaminants by combustion without removing heat by extraneous coolingmeans from the catalyst during its travel through said initialcombustion zone, admixing the partially regenerated catalyst with anadditional quantity of an oxygencontaining gas and cooled recycledregenerated catalyst and passing the resulting suspension through asubsequent regeneration Zone to burn off an additional amount of saidcontaminants.

4. The method of regenerating spent catalyst fouled with carbonaceouscontaminants which comprises moving the spent catalyst continuously andserially through a plurality of regeneration zones in contact withoxygen to effect combustion of carbonaceous contaminants, limiting thefraction of contaminants removed in one of said zones to an amountremovable by combustion without exceeding the maximum safe catalystregeneration temperature and without substantial removal of heat fromsaid zone by extraneous cooling means, removing another fraction of saidcarbonaceous contaminants by combustion in another of said zones underconditions wherein removal of heat by extraneous cooling mean-s isnecessary to prevent an excessive temperature rise in the catalyst, andcooling the catalyst undergoing regeneration in said latter Zone whilein said zone by contact with previously regenerated and cooled catalystto maintain the temperature thereof within required limits.

5. The method of regenerating spent catalyst fouled with carbonaceouscontaminants which compri-ses moving the spent catalyst continuously andserially through a plurality of regeneration zones in contact withoxygen to effect combustion of carbonaceous contaminants, limiting thefraction of contaminants removed in one of said zones to an amountremovable by combustion without exceeding the maximum safe catalystregeneration temperature and without substantial removal of heat fromsaid zone by extraneous cooling means, admixing cool regeneratedcatalyst with the catalyst partially regenerated in said first-mentionedzone, and treating the resulting catalyst mixture in another of saidzones under conditions such as to cause further substantial combustionof the carbonaceous contaminants and further regeneration of thepartially regenerated catalyst.

6. The method of regenerating spent catalyst fouled with carbonaceouscontaminants which comprises moving the spent catalyst continuously andserially through a plurality of regeneration zones, treating thecatalyst in one of said zones with oxygen to effect combustion ofcarbonaceous contaminants to an amount removable by combustion withoutexceeding the maximum safe catalyst regeneration temperature and withoutsubstantial removal of heat from said zone by extraneous cooling means,further treating said catalyst in another of said zones with additionaloxygen under conditions wherein removal of heat -by extraneous coolingmeans is necessary to prevent an excessive temperature rise in thecatalyst, and cooling the catalyst undergoing regeneration in saidlatter zone while in said zone by Contact with previously regeneratedand cooled catalyst to maintain the temperature thereof within requiredlimits.

7. The method of regenerating nely divided spent catalyst fouled withcarbonaceous contaminants which comprises moving the catalyst whilesuspended in an oxygen-containing gas continuously and serially througha plurality of regeneration zones to effect combustion of carbonaceouscontaminants, limiting the fraction of contaminants removed in one ofsaid zones to an amount removable by combustion without exceeding themaximum safe catalyst regeneration temperature and without substantialremoval of heat from said zone by extraneous cooling means, removinganother fraction of said carbonaceous contaminants by combustion inanother of said zones under conditions wherein removal of heat ducedinto said latter zone to maintain the temperature therein withinrequired limits.

10. The method of regenerating finely divided f spent catalyst fouledwith carbonaceous contaminants which comprises moving the catalyst whilesuspended in an oxygen-containing gas continuously and serially througha plurality of x regeneration zones to effect combustion of carbonaceouscontaminants, limiting` the fraction of contaminants removed in one ofsaid zones to an from said zone by extraneous cooling means, re-

by extraneous cooling means is necessary to prevent an excessivetemperature rise in the catalyst, and cooling the catalyst undergoingregeneration in said latter zone while in said zone by contact withpreviously regenerated and cooled catalyst to maintain the temperaturethereof Within required limits.

8. The method of regenerating finely divided spent catalyst fouled withcarbonaceous contaminants which comprises moving the catalyst whilesuspended in an oxygen-containing gas continuously and serially througha plurality of regeneration zones to effect combustion of carbonaceouscontaminants, limiting the fraction of contaminants removed in one ofsaid zones to an amount removable by combustion without exceeding themaximum safe catalyst regeneration temperature and without substantialremoval of heat from said zone by extraneouscooling means, removinganother fraction of said carbonaceous contaminants by combustion inanother of said zones under conditions wherein removal of heat byextraneous cooling means is necessary to prevent an excessivetemperature rise in the catalyst, withdrawing catalyst from saidlast-mentioned zone, thereafter cooling said withdrawn catalyst, andrecycling said cooled finely divided catalyst in suspension in anoxygen-containing gas to said last-mentioned zone to maintain thetemperature thereof at the desired level.

9. The method of regenerating finely divided spent catalyst fouled withcarbonaceous contaminants which comprises moving the catalyst whilesuspended in an oxygen-containing gas continuously and serially througha plurality of regeneration zones to effect combustion of carbonaceouscontaminants, limiting the fraction of contaminants removed in one ofsaid zones to an amount removable by combustion without exceeding themaximum safe catalyst regeneration temperature and Without substantialremoval of heat from said zone by extraneous cooling means,

moving another fraction of said carbonaceous contaminants by combustionin another of said zones under conditions wherein removal of heat byextraneous cooling means is necessary to prevent an excessivetemperature rise in the catalyst,

withdrawing regenerated catalyst from said latter zone, cooling saidwithdrawn catalyst, and returning said cooled catalyst to said latterzone to maintain the temperature thereof within required limits.

11. The method of regenerating finely divided spent catalyst fouled withcarbonaceous contaminants which comprises moving the catalyst whilesuspended in an oxygen-containing gas continuously and serially througha plurality of regeneration zones to eifect combustion of carbonaceouscontaminants, limiting the fraction of contaminants removed in one ofsaid zones to an amount removable by combustion without exceeding themaximum safe catalyst regeneration temperature and without substantialremoval of heat from said zone by extraneous cooling means, re-

moving another fraction of said carbonaceous contaminants by combustionin another of said zones under conditions wherein removal of heatmaintainv the temperature thereof at the desired emoving anotherfraction of said carbonaceous I level.

ARNOLD BELCHETZ.

REFERENCES CITED The following references are of record in the file ofthis patent:

`vlUNITED STATES PATENTS Number Name Date 2,078,951 Houdry May 4, 1937'2,253,486 Belchetz Aug. 19, 1941 2,305,569 Degnen Dec. 15, 19422,320,273 Gohr et al May 25, 1943 2,326,705 Thiele et a1 A'ug. 1o, 19432,341,193 Scheineman Feb. 8, -1944 2,373,008 -Becker Apr. 3, 19452,377,935 Gunness June 12, 1945

